Portable toilets are the most commonly used type of toilet in recreational vehicles and boats because of the minimum amount of space they require. However despite the better space utilization conventional portable toilet assemblies provide, they take up too much space for small vehicles and boats.
According to the present invention, a vacuum toilet assembly is provided which takes up a minimum of space so that it can fit in vehicles and boats where vacuum toilets were previously impractical, and an assembly which also provides minimum water usage. For example the toilet itself has a width of between 14 and 15 inches, a length of 18 to 20 inches, and a height of 11 to 16 inches. The ball valve for connecting the vacuum tank to the toilet during flushing is less than 2.5 inches in diameter (e.g. 2 inches) rather than the conventional 3 inches. While the amount of water usage will depend upon how long the discharge valve associated with the toilet is operated, typically a 2.5-3 gallon sized water tank is sufficient to normally accommodate four adults for a period of 9-10 hours, who are expected to generate waste which will approximately fill a 5 gallon waste tank; a water pump may deliver water to the toilet at a rate of no more than 2 gallons per minute. Also, the vacuum tank, waste tank, and water tanks can be vertically stacked so that they take up no more space than is typically provided in a hanging locker or closet, and the vacuum pump and vacuum tank may be combined in a single module for optimum space saving.
The waste tank is also relatively small in size, e.g. 5 gallons, and may have a dip tube and vent which allow--in combination with the particular connection of the vacuum pump thereto--the tank to be readily pumped out, and to allow discharge from the tank if the tank is full.
The plastic vacuum tank also is provided in a low volume configuration since it has flat sides, and is mounted directly to and nested with the vacuum pump, the flat sides having a wall thickness to deflection ratio which allows a non-cylindrical construction of the vacuum tank. The particular connection of the vacuum pump with respect to the vacuum tank and waste tank avoids conventional macerating pumps (which consume electricity at such a rate as to make them impractical for small boats or RV spaces), eliminates the need for a large waste tank by using vacuum to convey waste directly into the tank, and the chances of clogs at the outlet from the vacuum tank are minimized. Also, by the particular construction of duckbill check valves provided on opposite sides of the vacuum pump (having a particular wall thickness to sealing lip ratio) maximizes functionality of the pump.
According to one aspect of the present invention, a vacuum toilet assembly is provided which takes up a minimum of space yet has maximum operability, minimum water usage, and minimum chance of components clogging. The assembly comprises the following elements: A vacuum toilet having a waste discharge normally closed by a vacuum-tight valve; A manual actuator for the vacuum tight valve; A fresh water tank; A vacuum tank having an inlet and an outlet; A vacuum pump having an inlet and an outlet; A waste tank having an inlet; A first hose for connecting the waste discharge of the toilet, adjacent the vacuum-tight valve, to the vacuum tank inlet; Direct connection means for connecting the vacuum tank outlet directly to the vacuum pump inlet; A second hose for connecting the vacuum pump outlet to the waste tank inlet; and a conduit for connecting the fresh water tank to the vacuum toilet. The direct connection means preferably comprises a vacuum tight tubular connector in sealed relationship with an opening in the vacuum tank, which opening comprises the vacuum tank outlet; a tubular fitting integral with the vacuum pump removably connected to the vacuum tight tubular connector; and first and second check valves within or between the vacuum tight tubular connector and the integral tubular fitting.
At least one of the first and second check valves comprises a duckbill valve of maximum diameter of less than two inches, of elastomeric material (e.g. ethylene propylene) having side walls terminating in edges, with a generally "lipless" construction; and wherein the ratio of the thickness of the side walls to the edge is approximately 1:1. A third duckbill valve is also preferably provided between the vacuum pump outlet and the second hose also having this size and ratio.
The assembly also comprises a water pump for pumping water from the fresh water tank to the conduit, particularly a submersible centrifugal pump disposed within the fresh water tank. Typically the fresh water tank is located above the toilet, and has a cap releasably closing an opening therein; and the water pump is mounted to the cap and removable from the fresh water tank through the opening, and further comprising anti-siphon means associated with the water reservoir or conduit. The anti-siphon means comprises a small vent opening in the cap, and a small vent opening in the conduit between the pump and the cap within the fresh water tank. The water pump is preferably electrically operated, and the assembly further comprises an electrical switch controlled by operation of the handle for starting the water pump just before the handle moves the vacuum tight valve to an open position connecting the vacuum tank to the toilet discharge.
The vacuum pump is also preferably electrically operated, and a swivel connection between the second hose and the waste tank includes electrical contacts which disconnect the vacuum pump from a source of electrical energy when the swivel connection is moved to an electrical disconnect position with respect to the waste tank.
The waste tank, vacuum tank with vacuum pump, and fresh water tank are preferably stacked one above the other in order in a vertical stack, with the waste tank on the bottom and fresh water tank on top, the vacuum tank inlet and outlet and vacuum pump being at the bottom of the vacuum tank. A second fresh water tank may also be provided, stacked above the fresh water tank, with a liquid tight verticalspassage between them.
The waste tank has a bottom and a top, and a dip tube provided within the waste tank extends from adjacent the bottom to the top. The dip tube comprises a circular cross-section tube having a straight portion adjacent the top thereof, and a dog leg portion between the straight portion and bottom thereof, and terminated adjacent the waste tank bottom on the dog leg by a surface substantially perpendicular to the straight portion, so that the bottom opening of the dip tube is larger in area than the cross-sectional area of the circular tube, and is substantially oval in shape.
The waste tank preferably has flat walls yet is cost-effectively made out of plastic material, particularly high density polypropylene about one-quarter inch thick. It is possible to make such a tank having no visible deflection at a vacuum of about 25 inches of mercury as long as there is no more than 80 square inches of continuous flat surface forming a wall (i.e. not interrupted by an angle or the like). Thus, the waste tank may be rotocast or blow molded, having a one piece construction, and avoiding the costs associated with injection molding.
It is the primary object of the present invention to provide a low volume configuration vacuum toilet assembly, with minimum water usage, and minimum chance of clogging. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.